JP2007063989A - Cooling fan - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the air volume increasing/size-weight reducing effect by generating an air flow in a conventionally work-unperforming part even if a blade becomes short in response to an enlargement of a boss part in a cooling fan. <P>SOLUTION: This cooling fan 6 is composed of a nylon boss part 2 integrally insert-molded with a metallic spacer 4 and seven blades 3 extending in the outward direction from its part. A skew angle (about 30 degrees) retreating in the rotational direction of the cooling fan 6 is arranged in a connecting part (a root part of the blades) 3a to the boss part 2 of the blades 3, and a part 3c over the blade tip continuing with the connecting part 3a is formed at substantially right angles to the rotational direction (the skew angle of 0 degree). When comparing an air volume characteristic between a conventional product having an outer diameter of ψ 490 mm, the boss part of ψ 192 mm and the blade length of 149 mm and the cooling fan 6 having an outer diameter of ψ 490 mm, the boss part of 2ψ 212 mm and the blade 3 length of 139 mm, the same air volume is provided even when the blade length is shorter by 10 mm. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a cooling fan used in automobiles, household electric appliances, commercial electric appliances, and the like, and particularly relates to a cooling fan capable of improving the cooling capacity and reducing the size and weight.

  2. Description of the Related Art Conventionally, cooling fans used in automobiles, household appliances, commercial appliances, and the like have been required to have improved cooling performance and reduced size and weight. Taking an automobile cooling fan as an example, there is a demand for an improvement in cooling capacity by increasing the engine displacement, a reduction in mounting space, and a reduction in size and weight from the viewpoint of improving fuel consumption. In order to improve the cooling capacity of a cooling fan for automobiles, an engine that inhibits the flow of air is arranged behind the cooling fan. Therefore, in order to distribute the air efficiently, the air flows in the diagonal flow direction. However, in order to obtain such a mixed flow effect in a conventional axial fan, it is necessary to increase the mounting angle of the blade (blade) with respect to the boss, resulting in an increase in rotational torque and fan efficiency. There was a problem of lowering.

Therefore, in the invention described in Patent Document 1, in order to improve the cooling capacity by flowing air in the diagonal flow direction without increasing the blade mounting angle, the skew retreats with respect to the fan rotation direction toward the blade tip. The blade has a corner.
Japanese Patent Laid-Open No. 3-89000

  However, as a characteristic of the wind flow in the cooling fan for automobiles, when the vehicle is not running (zero wind interception), the flow in the complete axial direction toward the engine block cannot be considered, but rather it is a diagonal flow. It is considered that the expected effect cannot be obtained so that the specific effect is not described in 1. That is, if the front of the cooling fan has a low pressure loss as in the conventional automobile, the flow to the engine block is strong as described in Patent Document 1 above, and it is considered that there is an effect of a mixed flow fan. This is because the automobile is in a high pressure loss state and it is difficult to produce an axial flow from the pressure around the cooling fan and the centrifugal component due to the rotation of the cooling fan. Further, the mixed flow in the high pressure loss state increases the flow to the shroud surrounding the cooling fan, which may cause noise.

  Also, in the running state, the flow to the engine block becomes stronger as the incoming wind becomes larger. However, since the air volume due to the incoming wind is large, there is a question about the necessity of increasing the air volume due to the mixed flow. In addition, there is a case where it is necessary to increase the inner diameter of the boss part due to an increase in the size of the parts attached to the boss part of the cooling fan, and the dimension of the boss part is increased while maintaining the size of the entire cooling fan. It must also meet the demands of shortening the blade length and ensuring the conventional air volume.

  Therefore, the present invention can expect the effect of increasing the air volume and reducing the size and weight even in a high pressure loss state by generating a wind flow by a portion of the blade that has not been performing conventional work (or degrading performance), and the length of the blade can be expected. It is an object of the present invention to provide a cooling fan that can be reduced in length, can secure a conventional air volume, and does not generate excessive noise.

  A cooling fan according to a first aspect of the present invention is a cooling fan comprising a substantially cylindrical boss portion and a plurality of blades extending outward from the boss portion, wherein the root portion of the blade is A skew angle retreating with respect to the rotation direction is provided, and the skew angle is set to be zero or to advance with respect to the rotation direction from the middle toward the tip.

  According to a second aspect of the present invention, there is provided a cooling fan having a ring-shaped outer periphery made of metal, a deep-drawn spacer, a plastic substantially cylindrical boss portion that is insert-molded integrally with the spacer, and the boss A plurality of blades extending outward from the portion, the root portion of the blade has a skew angle that recedes with respect to the rotation direction, and the skew angle is zero or the rotation from the middle toward the tip It is set to move forward with respect to the direction.

  According to a third aspect of the present invention, there is provided the cooling fan according to the first or second aspect, wherein a range in which the backward skew angle of the root portion of the blade is provided is from the root of the blade to about 10% of the total length of the blade. Within the range of up to about 40%.

  According to a fourth aspect of the present invention, there is provided the cooling fan according to any one of the first to third aspects, wherein a skew angle of retreating with respect to the rotation direction provided at a root portion of the blade is about 15 degrees to about It is within the range of 35 degrees.

  According to a fifth aspect of the present invention, in the cooling fan according to any one of the first to fourth aspects, the skew angle that advances with respect to the rotational direction provided on the tip side of the blade is 0 degree to about 20 degrees. It is within the range.

  A cooling fan according to a sixth aspect of the present invention is the cooling fan according to any one of the first to fifth aspects, wherein one or two or more reinforcing ribs are provided in the radial direction at the root of the blade.

  A cooling fan according to a seventh aspect of the present invention is the cooling fan according to any one of the first to sixth aspects, wherein the reinforcing rib has 2 or more and 4 or less in the radial direction rearward with respect to the rotational direction of the root portion of the blade. Is provided.

  A cooling fan according to an eighth aspect of the present invention is the cooling fan according to the seventh aspect, wherein the reinforcing ribs of 2 or more and 4 or less do not protrude rearward from an extension line on the front end side on the rear surface side with respect to the rotation direction of the blade. It is provided.

  A cooling fan according to a first aspect of the present invention is a cooling fan including a substantially cylindrical boss portion and a plurality of blades extending outward from the boss portion, wherein the root portion of the blade is in the rotational direction. Is set so that the skew angle advances from zero to the rotation direction from the middle to the tip.

  The effect of the present invention will be described in comparison with FIGS. 8 and 9 showing the characteristics of a conventional cooling fan. FIG. 8 is a diagram showing the measurement of the wind flow on the negative pressure side (suction side) of a blade of a conventional cooling fan. FIG. 9 is a diagram showing the pressure distribution measured on the positive pressure side (blowing side) of a conventional cooling fan.

  As shown in FIG. 8, when the wind flow on the negative pressure side of the blade 13 where the skew angle is not provided in the conventional root portion is seen, the blade 13 of the blade 13 is originally shown as a small arrow 13b indicating the wind flow on the tip side. A flow toward the lower tip over the upper side is preferable. However, as indicated by a small arrow 13a at the root portion of the blade 13, the upward wind flow is swirled, and is indicated by four large arrows 13c. It is an unfavorable flow that disturbs the direction of the flow.

  Further, as shown in FIG. 9, in this figure, the portion closer to red (orange) has a higher pressure and the portion closer to blue has a lower pressure, but in the conventional cooling fan 11, the tip portion of the blade 13 is The pressure is highest in orange, and the pressure gradually decreases with yellow, green, and light blue as it approaches the base, and the boss portion 12 is blue and is almost close to atmospheric pressure.

  Thus, by providing a skew angle that recedes with respect to the direction of rotation at the root of the blade that is hardly useful for generating wind, but rather obstructs the preferred wind flow on the negative pressure side, the cooling fan is When rotated, the wind is forced to flow backward in the root of the blade. This helps to generate wind on the positive pressure side of the cooling fan, and a favorable wind flow also occurs on the negative pressure side, increasing the amount of air generated by the rotation of the cooling fan. Further, even if the blade length is reduced to reduce the size, an air volume equal to or higher than that of the conventional cooling fan 11 can be obtained, and the size and weight can be reduced.

  In this way, a cooling fan that can be expected to have an effect of increasing the air volume and reducing the size and weight even in a high pressure loss state by generating a wind flow by a portion of the blade that is not conventionally operated, and does not generate extra noise. It becomes.

  According to a second aspect of the present invention, there is provided a cooling fan comprising: a ring-shaped outer periphery made of metal, a deep-drawn spacer; a plastic substantially cylindrical boss portion that is insert-molded integrally with the spacer; and a boss portion. A plurality of blades extending outward, and the root of the blade is provided with a skew angle that recedes with respect to the rotation direction, and the skew angle is zero or with respect to the rotation direction from the middle toward the tip. It is set to move forward.

  A metal ring-shaped outer periphery with a deep drawing process, a plastic-made substantially cylindrical boss part that is insert-molded integrally with the spacer, and a plurality of blades extending outward from the boss part The cooling fan having the above is excellent in strength and can be reduced in weight. In addition, by providing a skew angle that recedes in the rotational direction at the root of the blade, it becomes useful to generate wind on the positive pressure side of the cooling fan, and a favorable wind flow also occurs on the negative pressure side, The amount of air generated by the rotation of the cooling fan increases. Furthermore, even if the blade length is reduced to reduce the size, an air volume equal to or higher than that of the conventional cooling fan can be obtained, and the size and weight can be reduced.

  In this way, it is excellent in strength and can be reduced in weight, and by generating wind flow by the part where the blade does not work conventionally, the effect of increasing the air volume and reducing the size and weight is expected even in a high pressure loss state. And a cooling fan that does not generate excessive noise.

  In the cooling fan according to the third aspect of the present invention, the range in which the skew angle at which the root portion of the blade recedes is provided is in the range from about 10% to about 40% of the blade total length from the blade base. This range is set as described above with reference to FIGS. 6 and 7 because the wind flow on the blade is undesirably affected by the low pressure around the boss portion.

  In this way, a cooling fan that can be expected to have an effect of increasing the air volume and reducing the size and weight even in a high pressure loss state by generating a wind flow by a portion of the blade that is not conventionally operated, and does not generate extra noise. It becomes.

  In the cooling fan according to the fourth aspect of the present invention, the skew angle retreating with respect to the rotation direction provided at the root of the blade is in the range of about 15 degrees to about 35 degrees. This is because if the angle is less than about 15 degrees, the backward skew angle is too small and the effect of increasing the air volume does not appear so much, and if it exceeds about 35 degrees, a forced wind flow due to rotation is generated unless the retreat area is enlarged. Because it becomes difficult. Therefore, by setting the skew angle that moves backward with respect to the rotation direction to be within a range of about 15 degrees to about 35 degrees, a forced wind flow due to the rotation is generated by moving the blade from the root to an appropriate region. The effect of increasing the air volume can be obtained with certainty.

  In this way, a cooling fan that can be expected to have an effect of increasing the air volume and reducing the size and weight even in a high pressure loss state by generating a wind flow by a portion of the blade that is not conventionally operated, and does not generate extra noise. It becomes.

  In the cooling fan according to the fifth aspect of the present invention, the skew angle that advances with respect to the rotation direction provided on the tip side of the blade is in the range of 0 degree to about 20 degrees. That is, the skew angle may be zero at the blade tip side, and is preferably about 20 degrees or less when a skew angle is provided to advance. As a result of earnest experimental research, the present inventor has found that the greatest effect of increasing the air volume can be obtained when the forward skew angle is in the range of 0 degrees to about 20 degrees. It has been completed.

  In this way, a cooling fan that can be expected to have an effect of increasing the air volume and reducing the size and weight even in a high pressure loss state by generating a wind flow by a portion of the blade that is not conventionally operated, and does not generate extra noise. It becomes.

  The cooling fan according to the invention of claim 6 is provided with one or more reinforcing ribs in the radial direction at the base of each blade. In order to reinforce the connection part of the blade with the boss part, that is, the root part of the blade, usually R is applied from the root part of the blade to the boss part. Since the skew angle is provided, if the R is added in this way, the root portion of the blade becomes extremely thick, which is contrary to the demand for weight reduction. Therefore, by providing one or more reinforcing ribs in the radial direction at the base portion of each blade instead of adding R, the root portion of the blade can be reinforced with little increase in the weight of the cooling fan.

  In this way, a cooling fan that can generate wind flow by a portion of the blade that is not conventionally used and can reinforce the root portion of the blade and improve durability without violating the demand for weight reduction. .

  The cooling fan according to the invention of claim 7 is provided with reinforcing ribs of 2 or more and 4 or less in the radial direction on the rear side with respect to the rotation direction of the root portion of the blade.

  By providing the reinforcing rib provided at the root portion of the blade on the rear side with respect to the rotation direction, the root portion of the blade can be more effectively reinforced. Further, if only one reinforcing rib is provided, the effect of reinforcement is small and the balance is deteriorated. On the other hand, if too many reinforcing ribs are provided, it is almost the same as providing R in weight, which is contrary to the demand for weight reduction. Therefore, by limiting the number of reinforcing ribs provided in the radial direction on the rear side with respect to the rotation direction of the blade root portion to 2 or more and 4 or less, the blade root portion is reinforced without substantially increasing the weight of the cooling fan. Can be achieved without fail.

  In this way, a cooling fan that can generate wind flow by a portion of the blade that is not conventionally used and can reinforce the root portion of the blade and improve durability without violating the demand for weight reduction. .

  The cooling fan according to the invention of claim 8 is provided so that the reinforcing ribs of 2 or more and 4 or less do not protrude rearward from the extension line on the front end side on the rear surface side with respect to the rotation direction of the blade.

  This makes it possible to increase the air volume more effectively without the reinforcement ribs provided in the radial direction on the rear side with respect to the rotation direction of the root portion of the blade without disturbing the wind flow.

  In this way, the wind flow is generated by the part of the blade that has not been used in the past, and the root of the blade is reinforced without violating the request for weight reduction and without disturbing the wind flow. The cooling fan can be improved.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1
First, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 is a plan view showing the overall configuration of the cooling fan according to the first embodiment of the present invention. FIG. 2 is a partially enlarged view showing one of the blades of the cooling fan according to the first embodiment of the present invention as viewed from the negative pressure side. FIG. 3 is a partially enlarged view showing one of the blades of the cooling fan according to the first embodiment of the present invention as viewed from the positive pressure side. FIG. 4 is a diagram showing the air flow characteristics of the cooling fan according to the first embodiment of the present invention in comparison with a conventional product. FIG. 5 is a diagram showing the noise characteristics of the cooling fan according to the first embodiment of the present invention in comparison with a conventional product.

  As shown in FIG. 1, the cooling fan 1 according to the first embodiment is made of a metal ring-shaped spacer 4 provided with mounting holes at four locations, and a plastic insert-molded integrally with the spacer 4. The cylindrical boss portion 2 and seven blades 3 extending outward from the boss portion 2 are configured. In the cooling fan 1 of the first embodiment, nylon is used as the plastic. Further, two reinforcing ribs 5 (naturally made of nylon) having different lengths extending from the outer periphery of the boss portion 2 are provided at the root portion of each blade 3. In the figure, the front side is the blade front edge side (air entering side).

  Next, a connection structure of the blade 3 to the outer periphery of the boss portion 2 will be described with reference to FIGS. As shown in FIG. 2, when viewed from the negative pressure side, a skew angle (about 30 degrees) retreating with respect to the rotation direction of the cooling fan 1 at the connection portion (blade root portion) 3 a of the blade 3 to the boss portion 2. ) And a skew angle (about 8 degrees) that moves forward with respect to the rotation direction is provided in the portion 3b that extends to the blade tip following the connection portion 3a. In addition, two nylon reinforcing ribs 5 having different lengths extending from the outer periphery of the boss portion 2 are provided at the base portion of the blade 3.

  FIG. 3 is a view from the positive pressure side, and a skew angle (about 30 degrees) retreating with respect to the rotation direction of the cooling fan 1 is also present at the connection portion (blade base portion) 3a of the blade 3 to the boss portion 2. A skew angle (about 8 degrees) that advances in the rotation direction is provided in the portion 3b that extends from the connecting portion 3a to the blade tip. The length of the portion 3 a provided with the backward skew angle is about 13% with respect to the entire length of the blade 3.

  The cooling fan 1 according to the first embodiment having such a structure was tested for air volume characteristics and noise characteristics as compared with a conventional cooling fan having a substantially similar structure. The conventional cooling fan is also composed of a metal ring-shaped spacer, seven nylon blades insert-molded integrally with the spacer, and a cylindrical boss portion connected to the outer periphery. The outer diameter is φ490 mm, the boss size is φ192 mm, and the blade length is 149 mm. On the other hand, the size of the cooling fan 1 according to the present embodiment is the same as the outer diameter dimension of φ490 mm, the dimension of the boss portion 2 is φ212 mm, and the length of the blade 3 is 139 mm.

As the measurement conditions, the air flow characteristics are measured using a static bath as a measuring device, and “JIS”
In accordance with the measurement method of “B 8330-81”, the measurement was performed for two levels of 1000 rpm and 2000 rpm. As for the noise characteristics, the sound pressure level at 1 m ahead of the fan was measured with a sound level meter while changing the fan rotation speed from 1000 rpm to 3000 rpm.

  As a result of the measurement test, the pressure diagram (air flow characteristic) is shown in FIG. 4, the cooling fan 1 according to the first embodiment has a fan 3 in spite of the fact that the length of the blade 3 is shortened by 10 mm. The airflow characteristics equivalent to those of the conventional products are shown at both of the two speeds of 1000 rpm and 2000 rpm. In addition, as shown in FIG. 5, the noise characteristics were reduced rather than the conventional products rather than being equal, and it was confirmed that they also had a low noise effect. In this comparative test, the outer diameter dimension was the same and the boss section dimension was increased, but when the boss section dimension was the same, the outer diameter (that is, the blade length) was decreased or the blade width was decreased. However, it is considered that the same or higher airflow can be obtained.

  As described above, in the cooling fan 1 according to the first embodiment, the wind flow is generated by the portion of the blade 3 that is not conventionally performing work, thereby increasing the air volume and reducing the size and weight even in a high pressure loss state. It can be expected and no extra noise is generated. Further, it is possible to meet the demand for increasing the size of the boss portion 2 and maintaining the size of the cooling fan 1 as a whole, and therefore shortening the length of the blade 3 and maintaining the air volume.

Embodiment 2
Next, a second embodiment of the present invention will be described with reference to FIGS. FIG. 6 is a perspective view showing the overall configuration of the cooling fan according to the second embodiment of the present invention. FIG. 7 is a partially enlarged view showing one of the blades of the cooling fan according to the second embodiment of the present invention as seen from the lateral direction.

  As shown in FIG. 6, the cooling fan 6 according to the second embodiment generally has the same configuration as the cooling fan 1 according to the first embodiment. That is, a metal ring-shaped spacer 4 provided with mounting holes at four locations, a plastic cylindrical boss portion 2 that is insert-molded integrally with the spacer 4, and extending outward from the boss portion 2. It consists of seven blades 3 that have been taken out. Also in the cooling fan 6 of the second embodiment, nylon is used as the plastic.

  Further, as shown in FIG. 7, similarly to the cooling fan 1 according to the first embodiment, when viewed from the negative pressure side, a connection portion (blade root portion) 3 a of the blade 3 to the boss portion 2 is included in the cooling fan. 6, a skew angle (about 30 degrees) retreating with respect to the rotational direction is provided, and a portion 3 c to the blade tip following the connecting portion 3 a is substantially perpendicular to the rotational direction (skew angle 0 degree). ). Similarly to the first embodiment, the length of the portion 3a provided with the backward skew angle is about 13% with respect to the entire length of the blade 3.

  The cooling fan 6 according to the second embodiment is different from the cooling fan 1 according to the first embodiment, as described above, in which the portion 3c extending to the blade tip following the connection portion 3a is substantially perpendicular to the rotation direction ( As shown in FIG. 7, two reinforcing ribs 7 having different lengths extending from the outer periphery of the boss portion 2 provided at the root portion of each blade 3 (of course, as shown in FIG. 7) Nylon) is provided so as not to protrude beyond the extension line 3d of the tip side 3c on the rear surface side with respect to the rotation direction of the blade 3.

  As a result, the Japanese reinforcing ribs 7 provided in the radial direction on the rear side with respect to the rotation direction of the root portion of the blade 3 can increase the air volume more effectively without disturbing the wind flow.

  The cooling fan 6 according to the second embodiment having such a structure was also tested for air flow characteristics under the same conditions as those in the first embodiment, as compared with a conventional cooling fan having a substantially similar structure. The conventional cooling fan is also composed of a metal ring-shaped spacer, seven nylon blades insert-molded integrally with the spacer, and a cylindrical boss portion connected to the outer periphery. The outer diameter is φ490 mm, the boss size is φ192 mm, and the blade length is 149 mm. In contrast, the cooling fan 6 according to the second embodiment has the same outer diameter as φ490 mm, the boss 2 has a dimension of φ212 mm, and the blade 3 has a length of 139 mm.

  As a result of the measurement test, the pressure diagram (air flow characteristics) shows that the cooling fan 6 according to the second embodiment has the fan rotation speeds of 1000 rpm and 2000 rpm, even though the blade 3 is shortened by 10 mm. The airflow characteristics equivalent to the conventional products were exhibited at any level.

  In this way, the cooling fan 6 according to the second embodiment generates a wind flow by the portion 3a of the blade 3 that is not conventionally used, and disturbs the wind flow without violating the request for weight reduction. The durability of the blade 3 can be improved by reinforcing the base of the blade 3. Further, it is possible to satisfy the demand for increasing the size of the boss portion 2 and maintaining the size of the cooling fan 6 as a whole, while reducing the length of the blade 3 and maintaining the air volume.

  In each of the above embodiments, the metal ring-shaped spacer 4, the seven plastic blades 3 which are insert-molded integrally with the spacer 4, and the cylindrical boss to which the blade 3 is connected to the outer periphery. Although the cooling fan 1 and the cooling fan 6 constituted by the part 2 have been described, in addition to this type of cooling fan, a cooling fan in which a synthetic resin part and a metal spacer are caulked with a bush, or all metal (iron or magnesium) is made. The present invention can also be applied to other types of cooling fans such as other cooling fans.

  Further, in each of the above embodiments, nylon resin is used as the plastic (the boss portion 2, the blade 3 and the reinforcing ribs 5, 7). However, the present invention is not limited to this, and polypropylene generally used for resin fans. In addition, other plastics (a plastic as a broad concept including not only a thermoplastic resin but also a thermosetting resin) can be used.

  Further, in each of the above-described embodiments, the number of blades (wings) 3 is seven, but is not limited to this.

  The configuration, shape, quantity, material, size, connection relationship, and the like of other parts of the cooling fan are not limited to the above embodiments.

FIG. 1 is a plan view showing the overall configuration of the cooling fan according to the first embodiment of the present invention. FIG. 2 is a partially enlarged view showing one of the blades of the cooling fan according to the first embodiment of the present invention as viewed from the negative pressure side. FIG. 3 is a partially enlarged view showing one of the blades of the cooling fan according to the first embodiment of the present invention as viewed from the positive pressure side. FIG. 4 is a diagram showing the air flow characteristics of the cooling fan according to the first embodiment of the present invention in comparison with a conventional product. FIG. 5 is a diagram showing the noise characteristics of the cooling fan according to the first embodiment of the present invention in comparison with a conventional product. FIG. 6 is a perspective view showing the overall configuration of the cooling fan according to the second embodiment of the present invention. FIG. 7 is a partially enlarged view showing one of the blades of the cooling fan according to the second embodiment of the present invention as seen from the lateral direction. FIG. 7 is a partially enlarged view showing one of the blades of the cooling fan according to the second embodiment of the present invention as seen from the lateral direction. FIG. 8 is a diagram of measuring the wind flow on the negative pressure side (blowing side) in the blade of a conventional cooling fan. FIG. 9 is a diagram showing the pressure distribution measured on the positive pressure side (suction side) of a conventional cooling fan.

Explanation of symbols

1,6 Cooling fan 2 Boss part 3 Blade 4 Spacer 5, 7 Reinforcement rib

Claims (8)

A cooling fan comprising a substantially cylindrical boss portion and a plurality of blades extending outward from the boss portion,
A cooling fan characterized in that a root portion of the blade is provided with a skew angle that recedes with respect to the rotation direction, and the skew angle is set to zero or to advance with respect to the rotation direction from the middle toward the tip. A spacer formed by deep drawing on a ring-shaped outer periphery made of metal, a substantially cylindrical boss portion made of plastic insert-molded integrally with the spacer, and a plurality of sheets extending outward from the boss portion A blade,
A cooling fan characterized in that a root portion of the blade is provided with a skew angle that recedes with respect to the rotation direction, and the skew angle is set to zero or to advance with respect to the rotation direction from the middle toward the tip.   The range in which a skew angle that recedes with respect to the rotation direction of the root portion of the blade is within a range from about 10% to about 40% of the blade total length from the root of the blade. The cooling fan according to claim 1 or 2.   4. The skew angle, which is provided at the root portion of the blade and recedes with respect to the rotation direction, is within a range of about 15 degrees to about 35 degrees. 5. Cooling fan.   The cooling according to any one of claims 1 to 4, wherein a skew angle that moves forward with respect to a rotation direction provided on a tip side of the blade is in a range of 0 degrees to about 20 degrees. fan.   The cooling fan according to any one of claims 1 to 5, wherein one or more reinforcing ribs are provided in a radial direction at a root portion of the blade.   The cooling fan according to any one of claims 1 to 6, wherein a reinforcing rib having 2 or more and 4 or less in the radial direction is provided on the rear side with respect to the rotation direction of the root portion of the blade.   8. The cooling fan according to claim 7, wherein the reinforcing ribs of 2 or more and 4 or less are provided so as not to protrude rearward from an extension line on the front end side of the rear surface side with respect to the rotation direction of the blade.

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